Fire alarm having fail safe bimetal-magnetic means



Tjec. 14, 1965 J. c. GIBSON 3,223,805

FIRE ALARM HAVING FAIL SAFE BIMETAL-MAGNETIG MEANS Filed May 16, 1962 CENTRAL ALARM SHIT/0N 10 /9 ALARM HORN 76 2/ fi l- //0 VOLT P/ M1. 0. sou/r05 LAMP l5J/6) FIG 3 22 23 54 70 I 0mm j SUBSTA T/ONS SUBSTA T ION INVENTOR. Jefferson 0. Gibson United States Patent 3,223,805 FIRE ALARM HAVING FAIL SAFE BIMETAL- MAGNETIC MEANS Jefferson C. Gibson, 217 E. Cullerton, Chicago, Ill. Filed May 16, 1962, Ser. No. 195,269 3 Claims. (Cl. 200-138) This application is a continuation-in-part of my application Serial No. 710,957, filed Jan. 1, 1958, which issued as Patent No. 3,036,294 on May 22, 1962.

The present invention relates to fire alarm systems and particularly to a monitoring substation for use in a fire alarm system.

It is an object of the present invention a simple and inexpensive fire alarm system of the type described wherein the central alarm station and the substations are continuously energized and wherein responsive to an abnormal temperature condition in any one of the substations, the central alarm station is operated to render both a visual and an audible alarm.

Another object of the invention is to provide thermostatic means at each of the substations which is adjustable to be responsive to different alarm temperatures and which when operated in response to an abnormal temperature condition is maintained operative thereafter despite gradient changes in the temperature from the abnormal temperature.

A feature of the invention is an improved fire alarm circuit provided with pilot lamps at the central station and at each of the substations illuminated under normal conditions of operation to indicate the monitoring state of the central station and of the substations.

An additional feature of the invention is the provision in each of the substations of a conductive bimetallic thermostat arrangement adjustable for different temperature ranges and which includes a magnetized contact plate completing a circuit with the temperature flexed bimetallic thermostat and maintaining such circuit in spite of gradient temperature changes tending to interrupt the circuit contact.

Another feature of the invention is the inclusion in the central alarm station circuit of a normally energized gravity solenoid which when deenergized completes a circuit for operating alarm devices.

Further objects and features of the invention pertain to the particular structure and arrangement employed in the invention whereby the above described objects are attained. The invention, both as to its structure and mode of operation, will be better understood by reference to the following specification and drawings, forming a part thereof, wherein:

FIG. 1 is a circuit diagram in schematic form of the fire alarm system;

FIG. 2 shows in detail the structure of and the circuit connections in each of the substations of the fire alarm system;

FIG. 3 shows in partial cross-section the structure of a gravity solenoid that may be employed in the circuit of the central alarm station; and

FIG. 4 shows in partial cross-section the structure of a spring loaded solenoid that may be employed in the circuit of the central alarm station.

Referring now to the drawings, there is shown in FIG. 1 a fire alarm system in accordance with the invention including a central alarm station and a plurality of monitoring substations including the substation 30. The central alarm station 10 includes an alarm lamp 13, a stepdown transformer 14, a pilot lamp 18, an alarm horn 19 and a solenoid relay 40 and a solenoid relay 70. Each of the substations such as the substation 30, includes a bi- 3,223,805 Patented Dec. 14, 1965 metallic thermostat 31, a magnetic contact 32 for the thermostat 31, and a pilot lamp 33.

Considering in detail the structure of the central alarm station 10, a llO-volt, 60-cycle source is applied to the primary winding 14a of the transformer 14 through conductors 11 and 12 and is extended in multiple from the conductors 11 and 12 to the alarm lamp 13 through conductors 44 and 48 and the normally closed contacts of the solenoid 40, here represented schematically by contacts 21. The secondary winding 14b of the step-down transformer 14 is center tapped and a circuit is completed from the center tap 51 via a conductor 15 through the pilot lamp 18 and a conductor 17 extending to a terminal end 52 of the winding 14b. In addition, a connection is com pleted from the terminal end 52 through the conductor 17, the alarm horn 19, a conductor 20, the winding of the solenoid relay 40, a conductor 21 and a conductor 16 to the other end terminal 53 of the secondary winding 14b. In this circumstance and without considering further connections from the central alarm station to the substations, the current flows between the center tap 51 and the end terminal 52 of the secondary winding 14b through the pilot lamp 18 thereby illuminating the lamp and a current flows between the terminals 52 and 53 of the secondary winding 14b in series through the alarm horn 19 and the winding of the solenoid relay 40. The solenoid 40 is energized in order to maintain the operating circuit for the alarm lamp 13 interrupted at the contacts 21, and the impedance of the energized solenoid is such that the current flow through the series connected alarm horn 19 is insufficient to operate the horn. Accordingly, in this circumstance, the pilot lamp 18 of the central alarm station 10 .is illuminated to indicate that the central alarm station is in monitoring operation and neither the alarm lamp 13 or the alarm horn 19 are operative.

The solenoid relay 70 which, as schematically illustrated in FIG. 1 includes the contacts 71, is connected across the secondary winding 14b to conductors 16 and 17, respectively, by conductors 73 and 72 so that the relay is energized and the contacts 71 are opened. A circuit including a conductor 75, a battery source 77, contacts 71 and a conductor 74 is connected across alarm horn 19 at conductors 17 and 20 for energizing the alarm horn when the solenoid relay 70 is deenergized and the contacts 71 are closed as by a power failure to the step-down transformer 14. In the circuit a switch 76 may be included for interrupting the circuit and preventing operation of the alarm horn 19.

Considering now the connection of the substations such as the substation 30 to the central alarm station 10, a conductor 22 is connected in multiple to the substations at the junction between the conductors 21 and 16 in the central alarm station and a conductor 23 is connected in multiple to the substations from the conductor 20 in the central alarm station. In the substations, as in the substation 30 a pilot lamp 33 is connected in series between the conductors 22 and 23, and in parallel with the lamp 33 is the normally opened circuit including the bimetallic thermostat 31 and the magnetic contact 32. The magnetic contact 32 is coated or plated with silver, gold, platinum, or the like to render it highly conductive. Under normal temperature conditions, the circuit between the bimetallic thermostat 31 and the magnetic contact 32 is opened so that the pilot lamp 33 is connected in parallel with the winding of the solenoid relay 40 in the central alarm station 10. Accordingly, the pilot lamp 33 is illuminated, thereby indicating that the substation 30 is in monitoring operation.

Assuming an abnormal temperature condition such as would cause the bimetallic plate 31 to complete a circuit at the magnetic contact 32 in the substation 30, a low impedance path is completed between the terminals 52 and 53 of the secondary winding 14b including the conductor 17, the alarm horn 19, the conductor 23, a bimetallic thermostat 31, the magnetic contact 32, conductor 22 and conductor 16. Accordingly, both the winding of the solenoid relay 40 in the central alarm station and the pilot lamp 33 in the substation 30 are shunted so that a large current flows through the alarm horn 19 thereby causing an audible signal to be emitted. At the same time the solenoid relay 40 is deenergized thereby completing the circuit between the conductors 11 and 12 for illuminating the alarm lamp 13. In this manner the audible and visible alarms in the central alarm stations are both operated to indicate that an abnormal temperature condition exists at one of the substations. The alarms will continue to operate throughout the period of the abnormal temperature condition, through gradient flucturations in temperature and even after the abnormal temperature condition has been corrected and until the contact between the bimetallic thermostat 31 and the magnetic contact 32 is broken. Thereupon, the low impedance path is interrupted, and the path through the winding of the solenoid 40 is again completed and the alarm lamp 13 and the alarm horn 19 are both rendered inoperative. Specific operation and construction of the substation 30 will be better understood from the following considerations.

As shown in FIG. 2, in each of the substations, such as the substation 30, the conductor 22 from the central alarm station 10 is terminated on a terminal 61 common to the magnetic contact 32. The conductor 23 extending from the central alarm station 10 is terminated in the substation on a terminal 62 which is connected by means of a strap 66 to a pivotal arm 63. The arm 63 is pivotally mounted on an axis 64 and carries thereon the bimetallic strip 31 having a curved portion 31a and a straight portion 31b. Also mounted on the arm 63 is the pilot lamp 33 supported at one of its terminals in a clip 65 completing a conductive connection with the arm 63 and connected at its other terminal by a conductor 67 to the substation terminal 61. In this manner a circuit is completed from the conductor 22 to the conductor 23 via the terminal 61, the conductor 67, the lamp 33, the support clip 65, the arm 63, the strap 66, and the terminal 62, whereby the pilot lamp 33 is illuminated when the central alarm station 10 is provided with energizing power. The arm 63 against which the free end 31b of the bimetallic strip 31 rests under normal temperature conditions is arranged in the substation 30 with regards to the magnetic contact 32 so as to be adjustable at various distances from the magnetic contact 32. Accordingly, the free end of the bimetallic strip 31 may be moved between close and remote positions in regards to the magnetic contact 32, presenting in the close position a condition where only a small temperature change is required to complete the circuit between the bimetallic strip 31 and the magnetic contact 32 and presenting a condition in the remote position where a relatively large change in temperature is required to complete the circuit. Calibrations may be provided as shown in FIG. 2 whereby the substation can be set to be responsive and to render tn alarm at various dilterent temperatures here shown to extend in a range between 85 and 200. Thus, assuming that the substation is set to be responsive to a temperature of 200 as shown in FIG. 2 and assuming a normal temperature of approximately 70, as the temperature within the area of the substation 30 increases to 200 the bimetallic strip 31 is gradually distorted in its portion 31a and along its straight surface to move the free end 31b thereof towards the magnetic contact 32. When the temperature of 200 or more is achieved, contact will have been completed between the metallic strip 31 and the magnetic contact 32 so that a circuit is completed between the conductors 22 and 23 via the terminal 61, the magnetic contact 32, the bimetallic strip 4: 31, the arm 63, the strap 66 and the terminal 62. The pilot lamp 33 is shunted and extinguished. Accordingly, an alarm is sounded at the central alarm station 10. This circuit is maintained completed as long as the temperature is above 200 and due to the magnetic attraction of the magnetic contact 32 a good circuit connection will remain maintained between the bimetallic strip and the magnetic contact even after the temperature in the area has dropped to considerably less than 200, for.

example, to 150. Thus the magnetic contact insures a good circuit connection between the contact and the bimetallic strip and causes the alarm condition to persist until in all certainty the abnormal temperature condition has subsided. The region of the bimetallic strip which engages the magnetic contact, may if desired, be coated or plated with silver, gold, platinum or the like.

For purposes of testing the operation of the central alarm station circuit and reproducing therein the same effects as would be created by an abnormal temperature condition at any one of the substations such as the substation 30, a test switch 73 is connected in parallel with the winding of the solenoid relay 40. Upon closing of the test switch 78 a low impedance path is completed between the terminals 52 and 53 of the secondary winding 14b including the conductor 17, the alarm horn 19, the conductor 20, the contacts of the test switch 78, the conductor 21 and the conductor 16. Accordingly, the winding of the solenoid relay in the central alarm station and the conductors 22 and 23 extending to the substations are shunted so that a large current flows through the alarm born 19 thereby causing an audible signal to be emitted. At the same time the solenoid relay 40 is deenergized thereby completing the circuit between the conductors 11 and 12 for illuminating the alarm lamp 13.

Considering the circumstance where a power failure to the central alarm station is experienced so that the alarm system is inoperative for rendering abnormal temperature alarms, provision is made for operating the alarm horn 19 Without illuminating the alarm lamp 13 to indicate the power failure condition. Specifically, with a power failure the windings or" the relays 40 and 70 are deenergized so that the contacts 21 and 71 are closed. Even though the contacts 21 are closed the alarm lamp 13 is not illuminated because of the lack of power. However, when the contacts 71 are closed the previously described circuit including the battery source 71 is completed across the alarm horn 19 and cause operation of the alarm horn. Operation of the alarm horn 19 without illumination of the alarm light 13 indicates power failure to the attendant at the central alarm station and alerts him that the fire alarm system is ineffective until power is restored.

The structural details of the one type of solenoid relay employed in both the relay 40 and the relay 70 of the central alarm station 10 is shown in FIG. 3. The solenoid relay structure shown therein is of the gravity type and includes a coil core 41 of insulated material joined at its ends to an insulator collar 42 and an insulator collar 43, respectively, by means of a cylindrical conductive shaft 49 extending through the coil core 41. At the collar end 42 a circuit conductor 54 is inserted into the cylindrical casing 49 and in conductive relationship therewith and at the collar end 43 a conductive screw or plug 47 having a circuit conductor 55 connected thereto is inserted in spaced apart relationship with the cylindrical casing 49. Carried in the cylindrical casing 49 between the conductor 54 and the plug 47 and in the approximate area of the coil core 41 is a conductive solenoid pin 46 slidable in the shaft with an insulating pad positioned between the conductor 54 and the solenoid pin 46. The winding 50 is carried on the coil core 41 and when the winding 50 is energized the solenoid pin 46 is carried in the casing 49 as shown in FIG. 3 approximate to the conductor 54. In this condition the circuit between the conductor 54 and the conductor 55 is incomplete. When the winding 50 is deenergized, the solenoid pin 46 drops from its proximate relationship to the conductor 54 and rests on the plug 47 thereby completing a conductive path between the conductor 54 and the conductor 55 via the cylindrical casing 49, the solenoid pin 46 and the conductive plug 47.

An alternative structure for the solenoid relays 40 and 70 employed in the central alarm station is shown in FIG. 4. The solenoid relay thereof is of a spring loaded type and includes all of the structural elements of the relay shown in FIG. 3 and in addition a helical spring 56. In this arrangement a circuit is completed between conductors 54 and 55 by action of the spring engaging the pin 46 against the plug 47. However, when the winding 50 thereof is energized, the pin 46 is withdrawn from contact with the plug 47 and the spring 46 is compressed as shown in FIG. 4 thereby interrupting the circuit between the conductors 54 and 55.

As previously explained, the windings of the solenoid relays 40 and 70 are normally maintained energized so that the circuits controlled thereby are normally incomplete. In the case of relay 70, the winding thereof is deenergized in response to a power failure to the central alarm station so that the contacts 71 are closed and the circuit completed for operating the alarm horn 19. In the case of relay 40, the winding thereof is deenergized in response to operation of the test switch 78 or an abnormal temperature conditions in one of the substations so that the contacts 21 thereof are closed and the circuit completed for operating the alarm horn 19 and illuminating the alarm lamp 13. It is to be understood that the alarm lamp 13 is merely illustrative of a group of alarm devices operative from the relay 40 and that fire doors, alarm sirens, remote indicators, etc. could also be operated under control of the relay 40.

The foregoing description has been given in detail without thought of limitation since the inventive principles in volved are capable of assuming other forms without departing from the spirit of the invention or the scope of the following claims.

What is claimed is:

1. A substation for a fire alarm system which is manually adjustable to be responsive to different alarm temperatures and which is maintained operative even after responding to said alarm temperatures whereby a nondestructive alarm mechanism is effected comprising, in combination, a first and a second terminal, said first terminal including a magnetic contact and said second terminal including a pivot means with a pivotal arm thereon with its free end being manually movable toward said magnetic contact, a temperature responsive element mounted upon the pivotal arm and movable toward and into engagement with said magnetic contact when exposed to a predetermined alarm temperature, said alarm temperature being predetermined by the distance of said pivotal arm from said magnetic contact, and said distance being adjustable by the movability of said pivotal arm about the pivot means, a pilot light electrically connected to said pivotal arm and in parallel circuit with said magnetic contact and said temperature responsive element, whereby said pilot light is continuously illuminated to indicate a monitoring condition for said substation.

2. A substation for a fire alarm system which is manually adjustable to be responsive to different alarm temperatures and which is maintained operative even after responding to said alarm temperatures whereby a nondestructive alarm mechanism is elfected comprising, in combination, a first and a second terminal, said first terminal including a magnetic contact and said second terminal including a pivot means with a pivotal arm thereon with its free end being manually movable toward said magnetic contact, a bimetallic strip, one portion of which is curved with one end thereof affixed to the pivotal arm near its pivot point, and another portion being straight with its end being movable about the pivot means toward and into engagement with said magnetic contact when said bimetallic strip is exposed to a predetermined alarm temperature, said alarm temperature being predetermined by the distance of said pivotal arm from said magnetic contact, and said distance being adjustable by the movability of said pivotal arm, a pilot light electrically connected to said pivotal arm and in parallel circuit with said magnetic contact and said temperature responsive element, whereby said pilot light is continuously illuminated to indicate a monitoring condition for said substation.

3. The substation of claim 1 wherein calibrations are provided under said pivotal arm for accurate adjustment of the pivotal arm relative to the magnetic contact, said calibrations being indicative of predetermined temperatures required for causing the temperature responsive element to move into engagement with the magnetic con tact.

References Cited by the Examiner UNITED STATES PATENTS 1,122,830 12/1914 Wiese 200-139 1,259,577 3/1918 Wolf 200-139 1,798,854 3/1931 Satchwell 200-138 2,282,197 5/1942 Maynard 200-122 2,322,235 6/1943 Howard 200-122 2,709,249 5/1955 Sperry 340-213 2,753,548 7/ 1956 Gates 340-221 2,858,631 11/1958 Jorick 200-167 3,041,104 12/1961 Corbine et a1. 200-113 BERNARD A. GILHEANY, Primary Examiner. NEIL C. READ, Examiner, 

1. A SUBSTATION FOR A FIRE ALARM SYSTEM WHICH IS MANUALLY ADJUSTABLE TO BE RESPONSIVE TO DIFFERENT ALARM TEMPERATURES AND WHICH IS MAINTAINED OPERATIVE EVEN AFTER RESPONDING TO SAID ALARM TEMPERATURES WHEREBY A NONDESTRUCTIVE ALARM MECHANISM IS EFFECTED COMPRISING, IN COMBINATION, A FIRST AND A SECOND TERMINAL, SAID FIRST TERMINAL INCLUDING A MAGNETIC CONTACT AND SAID SECOND TERMINAL INCLUDING A PIVOT MEANS WITH A PIVOTAL ARM THEREON WITH ITS FREE END BEING MANUALLY MOVABLE TOWARD SAID MAGNETIC CONTACT, A TEMPERATURE RESPONSIVE ELEMENT MOUNTED UPON THE PIVOTAL ARM AND MOVABLE TOWARD AND INTO ENGAGEMENT WITH SAID MAGNETIC CONTACT WHEN EXPOSED TO A PREDETERMINED ALARM TEMPERATURE, SAID ALARM TEMPERATURE BEING PREDETERMINED BY THE DISTANCE OF SAID PIVOTAL ARM FROM SAID MAGNETIC CONTACT, AND SAID DISTANCE BEING ADJUSTABLE BY THE MOVABILITY OF SAID PIVOTAL ARM ABOUT THE PIVOT MEANS, A PILOT LIGHT ELECTRICALLY CONNECTED TO SAID PIVOTAL ARM AND IN PARALLEL CIRCUIT WITH SAID MAGNETIC CONTACT AND SAID TEMPERATURE RESPONSIVE ELEMENT, WHEREBY SAID PILOT LIGHT IS CONTINUOUSLY ILLUMINATED TO INDICATE A MONITORING CONDITION FOR SAID SUBSTATION. 